package org.tln.modules.utils;

import java.io.UnsupportedEncodingException;
import java.util.Enumeration;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.TreeMap;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.tln.modules.utils.EncodeUtils;

/**
 * Http与Servlet工具类.
 *
 */
public class ServletUtils {

        //-- Content Type 定义 --//
        public static final String TEXT_TYPE = "text/plain";
        public static final String JSON_TYPE = "application/json";
        public static final String XML_TYPE = "text/xml";
        public static final String HTML_TYPE = "text/html";
        public static final String JS_TYPE = "text/javascript";
        public static final String EXCEL_TYPE = "application/vnd.ms-excel";

        //-- Header 定义 --//
        public static final String AUTHENTICATION_HEADER = "Authorization";

        //-- 常用数值定义 --//
        public static final long ONE_YEAR_SECONDS = 60 * 60 * 24 * 365;

        /**
         * 设置客户端缓存过期时间 Header.
         */
        public static void setExpiresHeader(HttpServletResponse response, long expiresSeconds) {
                //Http 1.0 header
                response.setDateHeader("Expires", System.currentTimeMillis() + expiresSeconds * 1000);
                //Http 1.1 header
                response.setHeader("Cache-Control", "private, max-age=" + expiresSeconds);
        }

        /**
         * 设置客户端无缓存Header.
         */
        public static void setNoCacheHeader(HttpServletResponse response) {
                //Http 1.0 header
                response.setDateHeader("Expires", 0);
                response.addHeader("Pragma", "no-cache");
                //Http 1.1 header
                response.setHeader("Cache-Control", "no-cache");
        }

        /**
         * 设置LastModified Header.
         */
        public static void setLastModifiedHeader(HttpServletResponse response, long lastModifiedDate) {
                response.setDateHeader("Last-Modified", lastModifiedDate);
        }

        /**
         * 设置Etag Header.
         */
        public static void setEtag(HttpServletResponse response, String etag) {
                response.setHeader("ETag", etag);
        }

        /**
         * 根据浏览器If-Modified-Since Header, 计算文件是否已被修改.
         *
         * 如果无修改, checkIfModify返回false ,设置304 not modify status.
         *
         * @param lastModified 内容的最后修改时间.
         */
        public static boolean checkIfModifiedSince(HttpServletRequest request, HttpServletResponse response,
                        long lastModified) {
                long ifModifiedSince = request.getDateHeader("If-Modified-Since");
                if ((ifModifiedSince != -1) && (lastModified < ifModifiedSince + 1000)) {
                        response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
                        return false;
                }
                return true;
        }

        /**
         * 根据浏览器 If-None-Match Header, 计算Etag是否已无效.
         *
         * 如果Etag有效, checkIfNoneMatch返回false, 设置304 not modify status.
         *
         * @param etag 内容的ETag.
         */
        public static boolean checkIfNoneMatchEtag(HttpServletRequest request, HttpServletResponse response, String etag) {
                String headerValue = request.getHeader("If-None-Match");
                if (headerValue != null) {
                        boolean conditionSatisfied = false;
                        if (!"*".equals(headerValue)) {
                                StringTokenizer commaTokenizer = new StringTokenizer(headerValue, ",");

                                while (!conditionSatisfied && commaTokenizer.hasMoreTokens()) {
                                        String currentToken = commaTokenizer.nextToken();
                                        if (currentToken.trim().equals(etag)) {
                                                conditionSatisfied = true;
                                        }
                                }
                        } else {
                                conditionSatisfied = true;
                        }

                        if (conditionSatisfied) {
                                response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
                                response.setHeader("ETag", etag);
                                return false;
                        }
                }
                return true;
        }

        /**
         * 设置让浏览器弹出下载对话框的Header.
         *
         * @param fileName 下载后的文件名.
         */
        public static void setFileDownloadHeader(HttpServletResponse response, String fileName) {
                try {
                        //中文文件名支持
                        String encodedfileName = new String(fileName.getBytes(), "ISO8859-1");
                        response.setHeader("Content-Disposition", "attachment; filename=\"" + encodedfileName + "\"");
                } catch (UnsupportedEncodingException e) {
                }
        }

        /**
         * 取得带相同前缀的Request Parameters.
         *
         * 返回的结果Parameter名已去除前缀.
         */
        @SuppressWarnings("unchecked")
        public static Map getParametersStartingWith(HttpServletRequest request, String prefix) {
                Enumeration paramNames = request.getParameterNames();
                Map params = new TreeMap();
                if (prefix == null) {
                        prefix = "";
                }
                while (paramNames != null && paramNames.hasMoreElements()) {
                        String paramName = (String) paramNames.nextElement();
                        if ("".equals(prefix) || paramName.startsWith(prefix)) {
                                String unprefixed = paramName.substring(prefix.length());
                                String[] values = request.getParameterValues(paramName);
                                if (values == null || values.length == 0) {//NOSONAR
                                        // Do nothing, no values found at all.
                                } else if (values.length > 1) {
                                        params.put(unprefixed, values);
                                } else {
                                        params.put(unprefixed, values[0]);
                                }
                        }
                }
                return params;
        }

        /**
         * 对Http Basic验证的 Header进行编码.
         */
        public static String encodeHttpBasic(String userName, String password) {
                String encode = userName + ":" + password;
                return "Basic " + EncodeUtils.base64Encode(encode.getBytes());
        }
}
